pea soup recipe

1 tablespoon olive oil - 1 large onion, chopped - 2 cloves garlic, minced - 2 cups dried green split peas, rinsed - 1 large carrot, chopped - 2 celery stalks, chopped - 1 potato, peeled and diced - 6 cups vegetable broth (or chicken broth) - 1 teaspoon dried thyme - 1 bay leaf - Salt and pepper to taste - Fresh parsley, chopped (for garnish)